 \begin{tikzpicture}[
node distance = 2cm and 2cm,
     N/.style = {circle, draw, font=\Large, 
                 minimum size=1.1em},
       every edge/.style = {draw, -Stealth, semithick, shorten >=2pt},
every edge quotes/.style = {auto=right, inner sep=2pt}
]
\node (m) at (0,0) {方法三:\color{red}确定式}; 
\node (n) at ([xshift=0em,yshift=-2em]m.south){$\mathrm{A}=\left\{a b^{n} c,(a b)^{n} \mid n \geqslant 0\right\}$};
\node (p)[align=center] at ([xshift=2em,yshift=-6em]m.south){$\divideontimes$确定的有限\\自动机如右图所示：};
\node[N] (a) at ([xshift=7em,yshift=-1em]n.south)[label=left :{+ -}] {1};
\node (h) at ([xshift=2em,yshift=-2em]a.south){\color{red}DFA:};
\node[N] (b)[right of=a] {2};
\node[N] (c)[right of=b]{3};
\node[N] (d) [below of=c]{6};
\node[N] (e) [right of=d]{7};
\node[N] (f) [right of=c]{4};
\node[N] (g) [right of=f]{5};
\path
(a) edge [above] node {a} (b)
(b) edge [above] node {b} (c)
    edge [bend left] node [above] {c} (g)
(c) edge [above] node {b} (f)
    edge [left] node {a} (d)
    edge [bend right] node [below] {c} (g)
(d) edge [above] node {b} (e)
(f) edge [above] node {c} (g)
    edge [loop above] node {b} ()
    % (e) edge [bend right] node [above] {b} (d)
(e) edge [bend right] node [above] {a} (d)
    ;
    \end{tikzpicture}